Hormonal control of growth in the infant rat.

Abstract

To obtain information on pituitary control of growth in infant rats, we employed a hypophysectomy technique which can be used on 4- to 6-day-old pups with an 80% success rate. A 30–50% reduction in body weight gain and a 30–40% decrease in tail growth were observed in the pups after hypophysectomy. The following hormone replacement injections were administered from days 7–15: ovine GH (oGH) or PRL (oPRL), at 1 or 4 μg/g BW, alone and in combination; T4 (40 ng/g for 4 days then 8 ng/g for 4 days) alone or in combination with the low dose of oPRL and/or oGH; and rat pituitary homogenate at 10 and 100 jug wet weight/g BW. Neither dose of oPRL increased weight gain or tail growth significantly. The high dose of oGH restored body weight gain and tail growth to 95% and 80%, respectively, of that in the sham controls. The low dose of GH increased both parameters to 75% of the sham values. Responses to injections of PRL and GH combined were intermediate between those of the hormones alone. T4 alone had no effect ...